Subscribe or Renew Membership Subscribe Renew

Shower Pan Waterproofing

Will's picture

*
I am confused about shower pan waterproofing. I have been told that the only IAPMO approved (I am told that there is no
UL or similar listing for this) shower pan liners are the ones made from PVC and similar materials. Yet, I constantly see
residential shower pans that have been hot mopped or torched down w/ modified bit. Furthermore, I also see alot of
products that are advertised as waterproof membranes for shower pans such as elastomeric coatings from several
manufacturers and also a product called Trowel & Seal (Custom Building Products). I am in the process of waterproofing a
couple of shower pans and do not want to go to the efforts of a full thickset mortar bed which would limit my choices to the
elastomeric coatings. What are people's opinions about any of these products or methods.?

(post #170910, reply #1 of 6)

*
I think the attributes of various waterproof techniques will be debated, with no "right" answer. There are several ways to do it. I would read Michael Byrne's book on the subject, and make up your own mind.

The key, and this is essential no matter what method you do use, is to create a sandwich of substrate which is covered on the bottom and the top with waterproof material. Usually the bottom is only tar paper, and the top is your main waterproofing material, be it a membrane, trowel on, copper, or even torch on roofing products. I think the expert's consensus is that the membrane is best, but when I was young and stupid, I used torch on and hot mop waterproofing, and they have lasted 15 years. So go figure! Good Luck.

(post #170910, reply #2 of 6)

*
Okay, Will, here's the deal. In the last 18 years I have replaced hundreds of shower pans. In fact, I have built a nice side business doing just this. The number one reason for replacement is leakage of the pan (duh).

Of all those pans, the biggest problem, ie, profits for me, is the hot mop. Only once have I replaced a vinyl pan, and that was because of vandalism by an irate carpenter.

My personal theory explaining this is that hot mop material is intended to lie flat, ie roof. When this material is placed in acute angles (floor/wall joint) it is going to fatigue and eventually crack, ergo water leakage.

I would think a material that remains pliable over time is the way to go. Hot mop material, once it cools, becomes brittle. Copper, etc. has too many seams and is harder to work. I don't feel good about introducing so many potential leaks (seams) and this material costs more.

Before you think I am only concerned with profit, let me say this: I like to sleep at night. The best way to asure this is to use the right material for the right job.

I suggest using either vinyl pan liner or Hydroment Ultra-Set. The former is intended for this use and is easy to work, although you will need to use a full mortar setting bed. You can set tile directly onto Ultra-Set, but must take some precautions.

One, when using Ultra-Set, wear some disposable gloves, you DO NOT want it on your skin, hairs, etc. Two, make sure you build a solid and secure subfloor, one with slope and as much rigidity as possible (you do not want a flexing floor). Three, skim coat the Utra-Set with thinset if you don't tile within 72 hours. After this, the tile will not bond to the Ultra-Set. Four, Use butyl rubber caulking at the drain to ensure good seal. Stick 1/8" dowels in the weep holes.

Hope this helps, rambling yours.

(post #170910, reply #3 of 6)

*
Sorry, one more thing; I'd be cautious re: something Tommy Mac said. In particular, he said, I'm paraphrasing, "to use your own judgement". I take it you desire advice because you don't have adequate knowledge here. Think 2nd story shower. Would you want to 'pick and choose' re: the information available. Me niether, perhaps you should get someone to do this part of the job for you. It would be the best $75 you ever spent. And you could sleep at night.

(post #170910, reply #4 of 6)

*
On our shower pans, we use a double system. We use
a vinyl membrane and Laticrete 9235 waterproofing.
The membrane is formed into a pan with folded
corners. Roofing felt covers the studs and overlaps
the membrane. Cement board is installed. The 9235
gets painted on with a special fiber tape in the
corners. This may be overkill -- but it is a lot
easier than tearing it out and doing it again lat

(post #170910, reply #5 of 6)

*
I also have replaced many failed pans, mostly lead and copper. I use Noble CPE on new and repair installations. They have pre-formed corner pieces that make the wall/curb junction easy to seal. The other materials in my area don't provide any special sealants or accessory pieces. The Noblesealant 150 is expensive, but once you use it once you won't use anything else.
I also use the tecnique that Micheal Byrne describes in his book as well as the article he wrote in the Journal of Light Construction in April 98.

(post #170910, reply #6 of 6)

*
I am confused about shower pan waterproofing. I have been told that the only IAPMO approved (I am told that there is no
UL or similar listing for this) shower pan liners are the ones made from PVC and similar materials. Yet, I constantly see
residential shower pans that have been hot mopped or torched down w/ modified bit. Furthermore, I also see alot of
products that are advertised as waterproof membranes for shower pans such as elastomeric coatings from several
manufacturers and also a product called Trowel & Seal (Custom Building Products). I am in the process of waterproofing a
couple of shower pans and do not want to go to the efforts of a full thickset mortar bed which would limit my choices to the
elastomeric coatings. What are people's opinions about any of these products or methods.?